Multiple contact electric switch



Nov. 18, 1947. c. o. BROWNE r-:TAL 2,431,023

MULTIPLE CONTACT ELECTRIC SWITCH Filed Feb. 1, 1944 2 sheets-sheet 1 Fig. 1.

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/A/x/E/vro/es. 626/1. 0. Bmw/w, deceased by MAMA/zar M Eeuw/vf, ci

[er/sr h4 727.45, Anm/suffrage) Allan/D. BI/u/nlearln/j Deceased lq TTOP/NEK Nov. 18, 1947. c. o. BROWNE ET AL 2,431,023

MULTIPLE CONTACT ELECTRIC SWITCH Filed Feb. 1, 1944. 2 sheets-sheet 2 Rigi/3.

did/L 0. Bkow/ve', deceased by Mmes/mir h4 zow/v) d?,

Patented Nov. 18, 1947 UNITED STATES PATENT OFFICE MULTIPLE CONTACT ELECTRIC SWITCH Application February 1, 1944, Serial No. 520,700 In Great Britain January 26, 1940 Section 1, Public Law 690, August 8, 1946 Patent expires January 26, 1960 Blumlein,

` 6 Claims. 1

The invention relates to multiple contact electric switches and more particularly to the application of such switches to effect connection to tapping points on impedances.

Arrangements, such as continuously variable potentiometers and stud switches, for eiecting electrical connections to a series of tapping points on an impedance are well known, but these arrangements have certain disadvantages when it is desired to employ a very large number of tapping points and high precision is necessary. If stud switches or the like are used, the large number of tappings and studs required give rise to practical diiculties, and continuously variable potentiometers cannot usually be adjusted with precision and are not always consistent in operation.

It is the object of the pre-sent invention to provide a multiple contact switch which will enable electrical connection eiTectively to be made to a relatively large number of tapping points by means of a relatively small number of contacts.

According to the present invention, multiple contact switch apparatus comprises a series of main contactsand means for making electrical connection with each of said main contact-s in succession, a series of auxiliary contacts and further means for making electrical connection with each of said auxiliary contacts in succession, said means and further means being electrically inter-connected and arranged for ysimultaneous operation in such a manner that as said further means is caused to pass over said auxiliary contacts, a conductor associated with said auxiliary contacts is operatively connected sequentially with a main contact and a sequence of a given number of auxiliary contacts.

In particular applications of the invention the multiple contact switch apparatus is arranged to eiect selection of desired values of resistive or reactive impedance and may be applied, for example, to a potentiometer arrangement, a time delay network or to an attenuator.

In order that the invention may be more clearly understood and readily carried into effect, such applications of `the invention will now be described in greater detail by way of example with reference to the accompanying drawings wherein Fig. 1 discloses a multiple contact switch according to one embodiment of the invention, and Fig.

executrix,

""'"2 discloses a multiple contact switch according I to another embodiment of the invention.

Referring to Figure 1 of those drawings, tappings on a rst impedance I are connected to contacts 2, which are spaced apart on three concentric circles, only parts of which are shown as rows A, B and C in the drawings. The length of each contact is arranged to be at least twothirds and preferably three-quarters of the distance d between the centres of adjacent contacts, and the spaces between adjacent contacts are preferably lled with insulating material, shown cross-hatched. Three brushes 3, 4, 5 spaced apart from each other on the switch arm (shown diagrammaticallyv at 9) by a distance equal to one-third of the distance between the centres of adjacent contacts 2 are arranged to slide over the contacts in the three rows A, B and C respectively. The brushes 3, 4, 5 are connected to slip rings 6, 'I and 8 respectively.

A second impedance III is tapped at intervals and the tappings are connected to contacts II which are spaced apart on a circular arcy three brushes I3, I4 and I5 set at an angle of 120 with respect to each other being arranged to rotate about a common axis so asto slide over the contacts II. The contacts II extend over an angle of approximately 240, so that as soon as one brush has passed oi the extreme right-hand element Ila, another brush passes on to the extreme lefthand element IIb, the remaining brush sliding over the centre contact IIc in the meantime. The brushes I3, I4, I5 associated with the second impedance are coupled respectively to the brushes 3, 4, 5 associated with the first impedance I by gearing I2 or otherwise in such manner that the brushes 3, 4, 5 move through a distance equal to the distance d between the centres of adjacent contacts 2 during one complete revolution of each of the brushes I3,v I4, I5. The brushes I3, I4, I5 are connected to three slip rings I5, I'I, I8 which are in turn connected to the slip rings 5, 1, 8 associated with the first impedance I, so that the brush I3 is connected to the brush 3, and so on. The contact I Ic is connected to the output or slider terminal 20.

The arrangement operates as follows. Let it be assumed that the brushes I3, I4, I5 are rotated clockwise from the position shown in the drawings.V In the position shown the output terminal 20 is connected via the slip rings I6 and 6 and the brush 3 to one of the elements 2 of the impedance I. As the brushes. I3, I4", I5 rotate,.the brush I5'y makes contact with the contact IIb, and that portion of the impedance III connected between the contacts IIb and IIc is connected in parallel with a pair of adjacent contacts 2Ak 0n the impedeand IIa is connected in parallel.. with the. above.

mentioned pair of adjacent contactsY 2. n the impedance I. As the brushes I3, I4, I rotate-in this manner, the output terminal 20 is, in efect,.

connected in turn to the elements oi aconstant impedance connected in parallel with one Aelement of the impedance I until when the brush I3`moves off the contact I Ia, it is connect'edto.the-tappingV point on the impedance I adjacent to the tapping:

point to which it was formerly connected. The brush I4, which has in the meantime been disconnected from the second impedance Io then makes' contact with the' contact IIb and cooperates with the brush I5 in'the'same manner as the brush I 5 previously cooperatedY with the brush I3. TheV result is thus'that a tapped impedance equal to one-half of the impedance Ill is connected in parallel with adjacent. tapping points'on the impedance I, and by means of the impedance III and the brushes I3, I4. I5, the intervals between successive tappingpoints on the impedance I are subdivided in turn without the necessity of 'a separate potentiometer for each. pair of tapping points. on the impedance I.

The impedance I may conveniently be provided Lwith three rows of 100 contacts 2, and each of these contacts may be three-eighths inch long and be spaced from each other by one-eighth inch. The impedance ID may be provided with twentyone contacts in all, only ten of which will be eifective at any given time, so that the impedance I may effectively be providedV with 3000 tapping points by the use of only 321 contacts, the maximum diameter of the apparatus being only 16".

Inorder to afford further sub-division, further impedances may be connected between the tapping points on the impedance Ill and the. contacts II to which they are connected and the dimensions of the brushes I3, I4, I5 and number and dimensions of the contactsl II are sochosen that one brush, for example, the brush I5 bridges two adjacent contacts II while brush I3 makes con.- tact with only one contactandrvice versa. When two adjacent contacts are. bridged' in this way, the bru-sh bridging them will then assume. a potential equal to the mean potential` of the two tapping points on the impedance I0 towhich the contacts are connected,v so thatv the number ofV tapping points on the impedance I0 is eiectively quadrupled.

If, on the other. hand, brushes I5 and I3 are so arranged that they can simultaneous-ly bridge two adjacent contacts II, the number, of. tapping points on the impedancev III iseffectively. doubled.

It will be appreciated that. if itis desired to give the potentiometerY a non-linear law. the im` pedance I should be tapped atfintervalsA sumf ciently close to ensure that the linear sub-division of those intervals by the impedance I0 and the brushes I3. I4, I5 will not give rise to any serious error in theY desired law. In such cases, if resistances are inserted in series with the tappings on the impedance I D and the contacts II, they should preferably be increased in value for the end contacts IIa and IIb, so that should all the brushes I3', I4, I5 momentarily make Contact with contacts I I, the output terminal will not tend to` assume the mean potential of two adjacent tappingV points on-the impedance I.

Although the impedances I and I0 will usually be resistances, if it is desired to divide a constant voltage, thesel impedances may be constituted by a tapped choke or a tapped condenser or other reactance whenlitis required to divide an alternating voltage. When tapped chokes are used, it isdesirable to include resistances between the tapping-points on the choke and the brushes I3, I4, I5 so as to avoid short-circuiting turns of the choke-.when any of these brushes bridge adjacent contacts I I. If desired, a condenser may be connected across the choke so as to increase the impedance which is connected in parallel with the adjacent elements. 2 of the impedance I. Alternatively, the number of contacts II may be increased so as to occupy a complete circle, a tappingon the impedance Illbeing connected to each contact I I as before, andthe slip rings 5, 'I, 8 permanently connected'to three equidistant tapping points on the impedance II), thebrushes I3, I4, I5' being removed. If now the output is taken from a brush moving over the contacts II, the voltage obtained from such a brush will be similar to that obtained from the terminal 20 in the arrangement described above. This alternative arrangement, although reducing the number of brushes re quired has, however, the disadvantage that it tends to place a larger load across the` impedance I, so that the impedance III has to be of a relatively high value if the law of the impedance' I is to be substantially unaffectedI by the shunting effect ofthe impedance I0.

If the impedance I is tapped so that the ratio of potential on any two consecutive contactsl 2`is the same for all pairs of contacts, the apparatus may b-e further simplied as will now'bedescribed with reference to Figure 2 of the drawings.

Referring to Figure 2, the impedance I which is shown as a time delay network, is tapped at equal intervals of time delay and the tappings are connected to contacts 2 which are spaced apart on two concentric circles, only parts of which are shown, asin Figure 1, as rows A and' B. Two brushes 3, 4 spaced apart from each other on the switch arm. shown diagrammatically at 9, are arranged to slide over the contactsdn rows A and B respectively and are connected to slip rings 6 and 1 respectively. The slip rings 5 and 'I are connected, if desired, each through a..

buffer valve 2I, to a second impedance, Illa, Illb respectively, each of said second impedances IIIa, IDb being, in the arrangement shown, a timede.- lay network terminated at its end remote from. the end operatively connected with the slip ring. 6 or 'I so as to prevent reflection. Each of the impedances IIIa, IIJb is provided with ten tapping points, and these tapping points are con nected to sets of contacts I Ia and I Ib respectively spaced apart on a circle. to rotate so as to pass over the two sets ofr contacts IIa, IIb in succession and is mechanically connected by gearing I2 or otherwise: with. the switch arm 9 in such manner that for one com.- plete rotation of the brush I3 the brushes 3, 4 move through a distance equal to the distance4 d betweenthe centres of the adjacent contactsl.k The brushes 3, 4 are spaced apart by half the distance d, so that as the switch arm 9 moves,

A brush I3 is arrangedone brush remains in contact with the same contact,fwhile the other changes from one contact to an adjacent contact. The second impedance Illa, I 0b is tapped at equal intervals, and the total time delay is arranged to be less by the time delay of one of said intervals than the diiference in time delay between adjacent tappings on the iirst impedance I.

The operation of the arrangement disclosed in Fig. 2 is as follows: With the brush I3 in the position shown in the iigure, the time delay corresponds to that of the tapping on the iirst impedance I to which the brush 3 is connected together with the additional delay introduced by two intervals of the second impedance Illa. As the brush I3 moves over the contacts IIa in a clockwise direction, the delay is successively increased, the brush 3 remaining in contact with the same contact in the row A of contacts associated with the first impedance I, but the brush 4 passing over the insulation between two adjacent contacts in the row B of contacts associated with the first impedance I. As the rotation of brush I3 continues, it passes off the extreme left-hand contact IIa on to the extreme left-hand contact IIb, by which time the brush 4 to which the latter contact is connected has made contact with the contact in row B connected to the next tapping in the rst impedance I. Further rotation of the brush I3 then adds the delay of the second impedance Ib by successive intervals until in due course the brush I3 passes on to the extreme right-hand contact II a and makes contact via brush 3 with the next adjacent tapping point on the rst impedance I and so on. It will be appreciated that each of the intervals on the second impedances Illa and I 0b must, in the example shown, be one-tenth of each interval on the rst impedance I, so that as the brush I3 passes from the extreme left-hand contact of the impedance I0a to the extreme left-hand contact of the impedance I Db, for example, the increase in time delay is equal to the increase in delay between adjacent contacts IIa or I Ib. A conductor connected to the brush I3 will therefore have a delay which can be adjusted by rotation of the brush I3, to intervals of one-tenth of the intervals between adjacent tapping points on the rst impedance I.

By replacing the reactive elements of the impedances I, IUa and I 0b by resistances, and adjusting the terminating resistances suitably, the arrangement which has just been described becomes an attenuator. If desired, the shunt resistances replacing the condensers of the time delay network may be omitted providing that the series resistances are graded so as to give the impedances Illa and Ib an exponential law.

Although the invention has been described with reference to voltage division and time delay by means of potentiometers and time delay networks respectively, it will be appreciated that the invention may be used generally for effecting electrical connection to a large number of contacts to which may be connected any desired kind of impedance or circuit.

What is claimed is:

l. Multiple contact switch apparatus comprising a plurality of sets of main contacts, each of said contact sets being arranged in a circle and the several contact sets being concentrically arranged in spaced relation, a plurality oi main contact brushes each individually associated with one of said contact sets and adapted to make electrical connection therewith in succession, a series of auxiliary contacts, a plurality of auxiliary contact brushes, equal in number to the main contact brushes, adapted to make electrical connection with said auxiliary contacts in succession, an electrical connection between each of the main contact brushes and a corresponding one of the auxiliary contact brushes, a conductor associated with the auxiliary contacts, and means for effecting continuous and simultaneous operation of the main and auxiliary contact brushes in timed relation such that as the auxiliary contact brushes pass over said auxiliary contacts said conductor is operatively connected sequentially with a main contact and a sequency of a given number of auxiliary contacts.

2. Apparatus according to claim 1 arranged to effect selection of desired values of an impedance wherein said main contacts are connected to tapping points in said impedance and said auxiliary contacts are connected to tapping points in an auxiliary impedance, the arrangement being such that at any given instant in operation, the portion of said auxiliary impedance between any selected number of auxiliary contacts is connected eifectively in parallel with a selected portion of said rst-mentioned impedance.

3. Apparatus according to claim 1 arranged to effect selection of desired values of a potentiorneter resistance wherein said main contacts are connected to tapping points in said resistance and said auxiliary contacts are connected to tapping points in an auxiliary resistance, the arrangement being such that at any given instant in operation, the portion of said auxiliary resistance between any selected number of auxiliary contacts is connected effectively in parallel with a selected portion of said rst-mentioned resistance.

4. Multiple contact switch apparatus comprising a plurality of sets of main contacts, the contacts of each set being of uniform length and arranged in a circle and the several contact sets being concentrically arranged in spaced relation, corresponding contacts, one in each set, being aligned in the axial direction, a rotatable switch arm provided with a set of brushes equal to the number of contact sets, said brushes upon rotation of the switch arm adapted each to make electrical connection with the main contacts of its associated set in succession, a series of auxiliary contacts, a switch member provided with a set of brushes equal to the number of switch arm brushes, an electrical connection between each pair of corresponding brushes, one in each set, a conductor associated with said auxiliary contacts, and means for effecting continuous and simultaneous operation of said switch arm and switch member in timed relation such that as the switch member brushes pass over the auxiliary contacts said conductor is operatively connected sequentially with a main contact and a sequence of a given number of auxiliary contacts.

5. The combination with an impedance, of which it is desired to effect the selection of a predetermined portion, of a plurality of sets of main contacts, the contacts of each set being of uniform length and arranged in a circle and the several Contact sets being concentrically arranged in spaced relation, corresponding "contacts, one in each set, being aligned in the axial direction, an electrical connection from each of said corresponding aligned contacts to successive, equally spaced tapping points on 'said impedance, a rotatable switch arm provided with a set of brushes,

one for each of said contacts sets, said brushes upon rotation of the switch arm adapted each to make electrical connection with the main contacts of its associated set in succession, a single set of auxiliary contacts, an auxiliary impedance provided with equally spaced tapping points electrically connected each to one of said auxiliary contacts, a switch member provided with a set of brushes equal to the number of switch arm brushes, an electrical connection between each pair of corresponding brushes, one in each set, and means for effecting continuous and simultaneous operation of said switch arm and switch member in timed relation such that at any given instant a selected portion of said auxiliary impedance is connected in parallel with that portion of said first impedance determined by the position of the switch arm brushes in relation to their respective main contacts.

6. The combination with an impedance, of which it is desired to effect the selection of a predetermined portion, of threeV spaced apart concentrically arranged sets of main contacts, the contacts of each set being of uniform length, insulated from one another and arranged in a circle, corresponding contacts, one in each set, 4being aligned in the axial direction, an electrical connection from each of said corresponding aligned contacts to successive, equally spaced tapping points on said impedance, a rotatable switch arm provided with a set of brushes one for each of said contact sets, said brushes upon rotation of the switch arm adapted each to make electrical connection with the main contacts of itsv associated set in succession, a single set of auxiliary contacts arranged in a partial circle and having less than the number of main contacts in any one set, an auxiliary impedance provided with equally spaced tapping points electrically connected each to one of said auxiliary contacts, a switch member provided with a set of three radially extending brushes only two of which are adapted to contact said auxiliary contacts at any instant, an electrical connection between each pair of corresponding brushes, one in each switch set, and means for effecting continuous and simultaneous operation of said switch arm and switch member brushes in timed relation such that for one complete revolution of the switch member brushes the switch arm brushes are moved a distance measured between the centers of adjacent main contacts, so that at any given instant a selected portion of said auxiliary impedance determined by the position of the switch arm brushes in relation to their respective main contacts.

MARGARET WINFRED BROWNE, ERNEST WILLIAM TOLE, Administrators of the Estate of Cecil Oswald Browne, Deceased.

DOREEN BLUMLEIN, Erecutrz'a: of the Estate of Alan Dower Blumlein,

Deceased.

REFERENCES CITED The following references are of record in the ile of this patent:

UNITED STATES PATENTS Number Name Date 2,085,255 Emlen June 29, 1937 2,114,143 Hunter Apr. 12, 1938 2,146,914 Rauhut Feb` 14, 1939 

